By Walter Pincus
Washington Post Staff Writer
Thursday, April 2, 1998; Page A03

Los Alamos National Laboratory, birthplace of the atomic bomb, for the first time in almost 40 years is preparing to produce plutonium triggers, key components of hydrogen bombs, as a way to keep warheads in the U.S. nuclear stockpile reliable and to prepare a reserve supply if additional weapons are built in the future.

The United States has halted production of new generations of nuclear weapons and stopped underground nuclear testing in 1992. President Clinton sent the Comprehensive Test Ban Treaty to the Senate last September for ratification.

However, the administration maintains a $4.5 billion annual program called "stockpile stewardship" that is designed "to insure a high level of confidence in the safety and reliability of nuclear weapons in the active stockpile," Department of Energy (DOE) Secretary Federico Peña told Congress last week.

The program includes building new elements for existing weapons, such as plutonium triggers, replenishing decaying nuclear materials in the weapons and designing new ways to test weapons components without conducting nuclear explosive tests that are banned by agreement or treaty.

The United States has seven weapons systems in its strategic nuclear stockpile, which totals about 7,000 warheads: the MX land-based ICBM, each with 10 warheads; the land-based Minuteman III ICBM with three warheads each; the Trident I and Trident II submarine-launched ICBMs with up to five warheads each; the Tomahawk cruise missile with one warhead; and the B-61 and B-63 nuclear bombs.

President George Bush withdrew all land-based tactical weapons, including some bombs, from Europe and the Far East in 1991, and shortly thereafter sea-based short-range nuclear devices from ships at sea.

The strategic stockpiled weapons have plutonium triggers, which are small atomic bombs that initiate a thermonuclear explosion of much greater power. Since plutonium is radioactive and changes over time, a handful are taken apart periodically for testing and then must be replaced.

The new triggers will also be available to form a war reserve "if it became necessary to rebuild the stockpile," according to Paul Cunningham, who heads the plutonium program at Los Alamos.

Another key aspect of the stewardship program involves tritium gas, the radioactive isotope of hydrogen, which is the critical element in all U.S. stockpiled nuclear fusion weapons.

DOE has not produced tritium for 10 years, but since tritium decays at 5.5 percent per year, the U.S. must continually replenish the tritium in the stockpiled weapons. For now, tritium requirements have been met by using tritium from warheads that are being dismantled. But to keep the strategic stockpile reliable, DOE has determined it must develop a new tritium production source by 2005, when the dismantling process will be coming to an end.

Peña told Congress last week that he will choose a new tritium source this year between Los Alamos, which has proposed a new type of accelerator system, and Savannah River, which would use a traditional, commercial light water nuclear reactor.

Another key part of the stockpile stewardship program is the $1.2 billion National Ignition Facility (NIF) under construction at Lawrence Livermore Laboratory. It will reproduce within a laboratory the conditions of temperature and density of matter close to those that occur in the detonation of nuclear weapons.

The NIF will give the United States the ability to study the behavior of matter and the transfer of energy and radiation in order to understand the basic physics of nuclear weapons and predict their performance without underground nuclear testing.

Although some foreign countries look on the stockpile program as a way for the United States secretly to develop new nuclear devices, Spurgeon Keeney, president of the Arms Control Association, a nonprofit group that advocates arms control, disagrees.

"I don't think there will be any new weapons produced by this program. Radical new developments such as X-ray or new fusion weapons would not be developed or fielded based on computer simulations and no one in the military or scientific community would certify weapons created in this way," Keeney said yesterday in an interview.